Tile Calculator: Tiles per m², Boxes and Grout

Estimate only. Check the product label and the building regulations where you live before you buy or build.

Quick answer

Divide the area by the space one tile takes up with its grout joint, add a waste allowance and round up. A 3 × 2.5 m floor is 7.5 m², and a 600 × 600 mm tile with a 3 mm joint takes up 603 × 603 mm, or 0.3636 m², so 20.6 tiles cover the floor. With 10% extra for cuts you buy 23 tiles.

How to use the tile calculator

Choose Room size and enter the length and width in metres. For an L-shaped room or several walls, split the space into rectangles and add each one as another area. If you already know the area in m², choose Total area. Switch to Imperial if you measured in feet.
Pick a tile size from the list, or choose Other size and type the size printed on the box. Then enter the joint width and pick the layout.
Open Box contents and waste to enter the tiles or the m² per box from the label. The waste allowance follows the layout; change it if your tiler uses a different figure.
For grout, enter the tile thickness and pick the bag size. If your grout’s data sheet gives a specific gravity, enter it under Grout density and extra.

How do you work out how many tiles you need?

Each tile takes up its own size plus one joint width in each direction, so a 600 × 600 mm tile with a 3 mm joint fills a 603 × 603 mm square of floor, which is 0.3636 m². Divide the area by that square, add a waste allowance for cuts and breakages, and round up to whole tiles and then to whole boxes.

Grout fills the joints, so the amount depends on how much joint there is per m² and how deep it is. Grout makers print the formula below on their data sheets, with the joint depth equal to the tile thickness. The calculator starts with a density of 1.5, the specific gravity given on BAL’s Micromax3 ECO data sheet.

area = length × width, added up for each rectanglespace per tile = (tile length + joint) × (tile width + joint)tiles = area ÷ space per tiletiles to buy = tiles × (1 + waste % ÷ 100), rounded upboxes = tiles to buy ÷ tiles per box, rounded upgrout in kg/m² = (L + W) ÷ (L × W) × joint width × joint depth × density, all lengths in mm

How many tiles and how much grout per m²?

Computed with the formulas above for 3 mm joints and a grout density of 1.5. The 200 × 200 mm tile is taken as 6 mm thick and the others as 9 mm, the thicknesses in BAL’s coverage table.

Tiles and grout per m² by tile size, 3 mm joints
Tile size	Tiles per m²	Tiles for 10 m² with 10% extra	Grout per m²
200 × 200 mm	24.27	267	0.270 kg
300 × 300 mm	10.89	120	0.270 kg
300 × 600 mm	5.47	61	0.203 kg
600 × 600 mm	2.75	31	0.135 kg

Grout weights are before any extra for mixing and cleaning. A wider joint or a thicker tile needs proportionally more grout.

Worked examples

600 × 600 mm tiles on a 3 × 2.5 m bathroom floor

The floor is 3 × 2.5 = 7.5 m². With 3 mm joints each tile takes up 603 × 603 mm, which is 0.3636 m², so 20.6 tiles cover the floor and 21 whole tiles is the minimum. A straight layout with 10% extra gives 23 tiles. If the box holds 4 tiles, that is 6 boxes, or 24 tiles.

For 9 mm thick tiles and a grout density of 1.5, the joints take about 0.14 kg of grout per m², 1.01 kg for the floor. With 10% extra for mixing and cleaning that is 1.11 kg, so one 2.5 kg bag is enough.

300 × 600 mm tiles on two shower walls

The walls are 1.2 m and 0.9 m wide and tiled to a height of 2.0 m. Enter them as Area 1 (1.2 × 2.0 m) and Area 2 (0.9 × 2.0 m), which add up to 2.4 + 1.8 = 4.2 m². With 2 mm joints, the minimum for walls, each tile takes up 0.1818 m², so 23.1 tiles cover the walls.

An offset of a third starts at 10% waste, so you buy 26 tiles, or 4 boxes if a box holds 8. For 9 mm thick tiles the grout comes to about 0.14 kg per m², the same as the floor above because the narrower joint balances the smaller tile. With 10% extra that is 0.62 kg, so one 2.5 kg bag.

How wide should grout joints be?

At least 2 mm on walls and 3 mm on floors. The Tile Association’s guide to tiling says wall tile joints must be at least 2 mm wide and floor tile joints at least 3 mm. BAL’s data sheet for its Micromax3 ECO grout gives the same minimums, quoting the British Standard guidelines, and adds that the size can change with the size of the tile and the setting. Pick wall or floor under Joint width check and the calculator tests your joint against that figure.

The same grout is made for joints from 1 mm to 30 mm, so the grout rarely limits the width. Where your tile maker asks for a wider joint, its instructions come first.

How accurate is the grout estimate?

It asks for about 8 to 9% more grout than one UK grout maker’s own table, which errs on the safe side. BAL’s coverage table for Micromax3 ECO gives 8.01 m² per kg for 600 × 600 × 9 mm tiles with 3 mm joints and 4.03 m² per kg for 300 × 300 × 9 mm tiles; the formula with BAL’s specific gravity of 1.5 gives 7.41 and 3.70 m² per kg.

BAL adds that coverage varies with the mixed grout and the way it is applied. If your grout’s data sheet has a coverage table, compare it with the rate the calculator shows (1 divided by m² per kg gives kg per m²) and adjust the density until they match.

Questions

How many tiles do I need per square metre?

With 3 mm joints you need 2.75 tiles of 600 × 600 mm per m², 5.47 tiles of 300 × 600 mm and 10.89 tiles of 300 × 300 mm. The joint adds to the space each tile takes up, so these counts are slightly lower than 1 m² divided by the tile’s face area (2.78, 5.56 and 11.11). Multiply by your area, add the waste allowance and round up to whole tiles and boxes.

How many tiles do I need for a 3 × 3 m room?

You need 28 tiles of 600 × 600 mm for a 3 × 3 m floor with 3 mm joints, including 10% for cuts. The floor is 9 m² and each tile with its joint takes up 0.3636 m², so 24.8 tiles cover it exactly. With 300 × 600 mm tiles the same floor takes 55 tiles, and with 300 × 300 mm tiles 108.

How much grout do I need per m²?

About 0.14 kg per m² for 600 × 600 mm tiles 9 mm thick with 3 mm joints, using the specific gravity of 1.5 on one UK grout’s data sheet. Smaller tiles have more joint per m²: 300 × 600 mm tiles need 0.20 kg and 300 × 300 mm tiles 0.27 kg at the same joint and thickness. Add an allowance for mixing and cleaning, and compare with the coverage table on your own bag.

What size grout joint should I leave for floor tiles?

Leave at least 3 mm on floors and 2 mm on walls. The Tile Association’s guide to tiling gives these minimums, and BAL’s grout data sheet repeats them from the British Standard guidelines, adding that the size can change with the tile size and the setting. The same grout fills joints from 1 mm to 30 mm. Where your tile maker asks for a wider joint, follow its instructions.

How much extra tile should I buy?

Buy about 10% more than the area needs for a straight or offset layout: The Tile Association, the UK trade body, advises allowing 10% extra for breakages and cutting, and says larger tiles may need more. The calculator starts diagonal layouts at 15% and herringbone at 20% because nearly every edge tile is cut; these are planning figures, not a standard. Keep any spare tiles for future repairs.

How many boxes of tiles do I need?

Divide the tiles to buy by the number in a box and round up: 23 tiles in boxes of 4 is 6 boxes, which hold 24 tiles. If the box gives m² instead, divide the face area of the tiles you need by that figure. Read the count on your own box, because the calculator’s starting figure of 4 is only a placeholder.

Sources

BAL (Building Adhesives Ltd), BAL Micromax3 ECO technical data sheet (checked 19 October 2026)Minimum joints of 2 mm for walls and 3 mm for floors per the BS guidelines; joints 1 to 30 mm; specific gravity 1.5; 2.5, 5 and 10 kg packs; coverage table.
BAL (Building Adhesives Ltd), BAL Micromax3 ECO (checked 19 October 2026)Pack sizes and joints from 1 mm to 30 mm.
Cégécol (Sika France), CARROJOINT PREMIUM data sheet (checked 19 October 2026)Grout consumption formula (L + l) × joint width × depth × density ÷ (L × l).
The Tile Association, Tile It Right: the essential guide to tiling (checked 19 October 2026)Joints at least 2 mm on walls and at least 3 mm on floors; allow 10% extra for breakages and cutting, more for larger tiles; extras kept for repairs.

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